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We use 25 years of a high‐resolution ocean reanalysis (1/12°) to revisit the Malvinas Current (MC) from the South (Drake Passage) to the North (Brazil‐Malvinas Confluence) from the synoptic to interannual time scales. The Malvinas Plateau is home to active eddy mixing, eddy dissipation and deep winter mixed layers occasionally reaching 600 m depth. The MC is organized in two jets which merge around 44°S as the continental slope steepens. The upper 900 m transport mean decreases from 40 Sv at 51°S to 35 Sv at 41°S indicating offshore leakage along the MC path. The MC plays a minor role in the velocity variations observed at the Confluence at seasonal and interannual scales; those are driven by changes in the intensity of the Brazil Current over the slope (34–36°S). Computing MC transport time series at different latitudes requires care because the section eastern limits are embedded in an energetic region. Transport time series were produced at selected latitudes using different criteria and showed common features. They show little seasonality (relative seasonal standard deviation of 2%) and no significant trend. The MC is a steady current: the relative standard deviation is on the order of 10% increasing to 20% near and on the Malvinas Plateau and near the Confluence. In contrast, velocity trends are large in the Brazil Current with the overshoot migrating southward. The associated increase in mesoscale activity south of 44°S in the Argentine Basin might contribute to blocking events occasionally reducing the MC transport. Plain Language Summary: The Malvinas Current (MC) is a branch of the Antarctic Circumpolar Current and flows northward along the Patagonian slope. We revisit the MC upper circulation and water masses using a high‐resolution ocean reanalysis from 1993 to 2017. The MC is a strong and rather steady current with little seasonality and no significant trend. The mean MC volume transport reduces from south to north by about 14%, indicating an offshore leakage along its path. The upper 500 m MC water underwent a freshening of 0.1 psu/decade. Key Points: The Malvinas Current is rather steady: Volume transport time series have little seasonality, no trend, and small relative standard deviationsThe upper 900 m transport mean decreases from 40 Sv at 51°S to 35 Sv at 41°S indicating offshore leakage along the MC pathThe Malvinas Plateau is a key region for water mass modification through eddy mixing and deep winter mixed layers [ABSTRACT FROM AUTHOR]

The Patagonian slope hosts a variety of waves. We used a state‐of‐the‐art ocean reanalysis to examine waves at the shelf break and in the core of the Malvinas Current (MC) at periods larger than 10 days. Statistics over 25 years indicated three types of signals: in phase signals at specific locations of the shelf break to the south of 47°S; fast propagating signals all along the shelf break (phase speed from 140 to 300 cm/s) at periods between 5 and 110 days; and slower signals in the core of the MC (phase speeds from 10 to 30 cm/s) at 20‐day, 60‐day, and 100‐day periods. The large zonal wind stress variations south of 47°S forced in‐phase along‐slope velocity variations and triggered fast propagating waves at distinct sites corresponding to abrupt changes in the shelf‐break orientation. The shelf‐break waves modulated the intensity of the inshore jet, which varied from 0 to 30 cm/s at 100 m depth, and had spatial and temporal structures and scales consistent with those of observed upwelling events. Slow propagating waves in the core of the MC had along‐slope wavelengths between 450 and 1,200 km and were not forced by the local winds. They were tracked back to the Drake Passage and the Malvinas Escarpment. Plain Language Summary: The sinuous Patagonian slope hosts a variety of waves that are yet poorly documented. We examined the waves in a state‐of‐the‐art ocean model assimilating observations. Strong westerly winds forced fast waves at the shelf break. These waves modulated the intensity of the coastal jet of the Malvinas Current (MC) and the shelf‐break upwelling. Slow waves propagating from the Malvinas Escarpment and the Drake Passage modified the velocities of the MC main jet. Key Points: Velocity signals with phase speeds of 140–300 cm/s at the shelf break and 10–30 cm/s in the core of the Malvinas Current (MC) were identifiedAt the shelf break, wind‐forced fast waves modulated the inner MC jet and possibly contributed to upwellingSlowly propagating waves in the core of the MC came from the Malvinas Escarpment or the Drake Passage [ABSTRACT FROM AUTHOR]

Twenty‐five years of high‐resolution (1/12°) ocean reanalysis are used to examine the Confluence of the Malvinas Current (MC) with the Brazil Current (BC) from synoptic to interannual time scales. The model transports of the MC (38.0 Sv ± 7.4 Sv 57 at 41°S) and the BC (23.0 Sv ± 11 Sv at 36°S) agree with observations. The model shows the branching of the MC near the Confluence with an offshore branch returning south and an inner branch sinking below the BC and managing to continue northward along the continental slope. Northward velocities associated with the subsurface inner branch peak at 40 cm/s at 36°S at 700‐m depth. The model documents the migrations of the Subantarctic (SAF) and Subtropical Fronts (STF) at the Confluence. The SAF and STF positions vary over a large range at synoptic (800 km) and interannual scale (300 and 200 km, respectively) compared to the rather small seasonal migrations of the STF (150 km) and SAF (50 km). While trends in the MC are small over the 25 years of the reanalysis, the BC becomes more intense (12.5 cm/s), saltier (0.37 psu), and warmer (2.5°C) in the upper 1,000 m. These trends are accompanied with a southward displacement of the STF and the SAF of 150 and 50 km. Plain Language Summary: The Brazil‐Malvinas Confluence is a highly dynamic region. Reproducing the circulation at the Confluence is a stringent test for operational models. Mercator Ocean high‐resolution (1/12°) ocean systems show remarkable performance in this region. We took advantage of 25 years of ocean reanalysis to examine variations in the Malvinas Current at 41°S, in the Brazil Current at 36°S, and in their confluence. The Malvinas Current branches at the Confluence: one branch veers offshore while the inner part subducts and flows north along the slope. At the Confluence, the Subantarctic and Subtropical Fronts show large synoptic (800 km) and interannual migrations (300 km) compared to rather small seasonal changes (<150 km). Key Points: Twenty‐five years of Mercator Ocean reanalysis are examined at the Brazil Malvinas Confluence from synoptic to interannual time scalesThe Malvinas Current branches at the Confluence: the outer part veers offshore, the inner part subducts, and flows north along the slopeThe migrations of the Subtropical and Subantarctic Fronts are large (small) at the synoptic and interannual (seasonal) time scales [ABSTRACT FROM AUTHOR]

Downstream of Drake Passage, the northern branches of the Antarctic Circumpolar Current, the Polar Front and the Subantarctic Front, veer northward and the latter forms the Malvinas Current (MC). The MC flows along the continental slope up to 38°S where it loops southward as the Malvinas Return Flow. Using 24 years of Mercator Ocean physical reanalysis outputs and Argo float data, we explore the open‐ocean side of the MC. We observe the occurrence of blocking events at 49°S, a region where the MC is exposed to the warm and salty anticyclonic anomalies propagating westward along the steep slope of the Malvinas Escarpment. During these events, the MC is cut off from its source, and the MC transport is considerably reduced at 49°S. The open‐ocean side of the MC is regularly supplied with cold polar waters from the Polar front.The polar waters accumulate and recirculate between the MC and the Malvinas Return Flow. The water characteristics of the recirculation region change over time. The recirculation region hosts significantly lighter and fresher waters during the period 1997–2003 compared with prior and later years. The 1997–2003 salinity minimum in the recirculation region corresponds to a period with reduced feeding events at 49°S. Plain Language Summary: The Malvinas Current (MC) is an extension of the Antarctic Circumpolar Current. It flows along the Argentinean continental slope up to 38°S where it performs a sharp cyclonic loop and turns to the south as the Malvinas Return Flow. We show that recurrently, the open‐ocean side of the MC is supplied with cold polar waters north of 49°S. These waters accumulate and recirculate between the MC and the Malvinas Return Flow. Blocking events at 49°S cut off the MC from the Antarctic Circumpolar Current. Twenty‐four years of Mercator Ocean physical reanalysis outputs show recurrent blocking and feeding events and subsequent recirculation cells. Salinity in the recirculation region showed a minimum in the water column in the 1997–2003 period. The salinity minimum corresponds to a change in the occurrence of feeding and blocking events. Key Points: Polar waters recurrently feed a cyclonic recirculation region north of 49 degrees south on the open‐ocean side of the Malvinas CurrentThe three‐dimensional structure of blocking and feeding events at 49 degrees south is characterized for the first timeA 1997‐2003 salinity minimum observed in the recirculation region corresponds to a period with reduced feeding events at 49 degrees south [ABSTRACT FROM AUTHOR]

Abstract: We examine the surface and subsurface signature of ocean fronts closely associated with the Malvinas Current dynamics. We first evaluate the performances of the Mercator Ocean eddy permitting (1/12° spatial resolution) global operational system in the southwestern Atlantic Ocean over the last 10 years (2007–2016) using satellite, Argo float and in situ data collected near 41°S. Observations versus model comparisons show that the model correctly reproduces the general circulation and the complex hydrographic features of the study area including the vicinity of the Brazil‐Malvinas Confluence. The model outputs accurately match the observations except in June 2015. The causes for the June 2015 mismatch are analyzed. We then used the model and satellite altimetry to identify isolines of absolute dynamic topography (ADT) and potential density at different depths associated with the mean front location and establish their correspondence with specific water mass boundaries. Frontal displacements as depicted in satellite ADT, model ADT, and model potential density at 450 m are in general agreement. The ADT and potential density at 450 m provide nonidentical and complementary information on eddies shed by the Polar Front (PF): while ADT depicts the surface circulation with PF eddies entrained into the energetic circulation over the deep Argentine Basin, potential density at 450 m is more effective at monitoring PF eddies feeding the Malvinas Current. [ABSTRACT FROM AUTHOR]